Roller lifter for internal combustion engine

ABSTRACT

A roller lifter for internal combustion engines is provided, which has higher rigidity of the lifter body, prevents cocking in the cylinder, and can achieve a size reduction. The roller lifter includes a cylindrical lifter body having a sliding surface on an outer circumferential surface thereof and a roller rotatably attached to the lifter body via an axial support pin and making contact with a rotating cam lobe. The lifter body includes a pair of support portions supporting the axial support pin. The axial support pin is mechanically fastened to the pair of support portions, with both ends thereof inserted in support holes formed in the support portions. The lifter body includes an anti-rotation retainer extending radially outward from the sliding surface. The sliding surface is formed on both front and rear sides in the sliding direction of the anti-rotation retainer.

CROSS-REFERENCE

This application claims priority to Japanese patent application no.2012-138596 filed on Jun. 20, 2012, the contents of which are entirelyincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a roller lifter for internal combustionengines used in car engines or the like.

BACKGROUND ART

There are known pump lifters used for fuel supply pumps or valve liftersused for valve gears in internal combustion engines such as car enginesor the like.

Some of these lifters include a roller at a portion directly contactinga cam lobe provided in fuel supply pumps or valve gear to reducefriction resistance against the cam lobe and to improve wear resistanceof the surface contacting the cam lobe (hereinafter referred to as“roller lifter 9”).

The roller lifter 9 is configured, as shown in FIG. 12, with a roller 93attached to a lifter body 92 having a sliding surface 924 that slides onthe inner wall of a cylinder in which the roller lifter 9 is installed.To fabricate the roller lifter, the roller 93 is first placed between apair of support portions 921 provided to the lifter body 92. An axialsupport pin 94 of the roller 93 is inserted into support holes 922formed in the support portions 921, and both ends of the axial supportpin 94 are compressed using a hydraulic press or the like to deform theends to increase their diameters, to mechanically fasten the axialsupport pin 94 to the support portions 921.

The roller 93 of the roller lifter 9 and the cam lobe are arranged suchthat their respective rotation axes are parallel, so as to minimizefriction resistance between the roller and the cam lobe. For thisreason, the lifter body 92 of the roller lifter 9 is formed with ananti-rotation retainer 923 to prevent displacement of the rotation axisof the roller 93, i.e., to prevent the lifter body 92 from rotatingrelative to the inner wall of the cylinder (see Patent Document 1).

This anti-rotation retainer 923 is formed at one axial end of the lifterbody 92 by cutting and bending processes using, for example, a cuttingtool or a press. More specifically, the anti-rotation retainer 923 isformed by cutting off part of one end of a cylindrical metal member toform a protruding piece of a predetermined size axially protruding fromone end of the lifter body 92, and by bending the protruding piece toprotrude radially outward.

The protruding piece needs to be bent largely outward in the radialdirection from inside. Therefore, the radial part of the lifter body 92opposite the protruding piece had to be largely cut off, except for thesupport portions 921, to form the anti-rotation retainer 923, as shownin FIG. 12.

PATENT DOCUMENT Patent Document 1: JP-A-2010-1884 SUMMARY OF THEINVENTION

However, the roller lifter 9 shown in Patent Document 1 may have lowerrigidity because part of the cylindrical metal member that is thecomponent forming the lifter body 92 is largely cut off as mentionedabove. Accordingly, there is a possibility that the lifter body 92 maydeform when the axial support pin 94 is mechanically fastened to thesupport portions 921, and the circularity accuracy of the slidingsurface 924 may be lowered.

Moreover, as the lifter body 92 is largely cut off by cutting andpressing as mentioned above, the lifter body 92 tends to have a smalllength in the front to back direction (axial direction) of the regionwhere the sliding surface 924 is formed. That is, the distance betweenthe front end and the rear end of the sliding surface 924 (hereinafterreferred to as “sliding length”) tends to be short. This may result inlarge cocking (wobbling) in the cylinder when the roller lifter 9 isinstalled in an internal combustion engine. Namely, the shorter thesliding length is, the larger the maximum inclination angle of thelifter body 92 becomes relative to the sliding axis, when the rollerlifter 9 is installed in an internal combustion engine. The surfacepressure between the lifter body 92 and the inner wall of the cylindertends to be larger accordingly, and the increased friction resistancemay impede smooth sliding of the roller lifter 9.

To prevent the cocking in the cylinder, it is conceivable to design thelifter body 92 to have a longer sliding length in the sliding surface924. However, in a configuration in which the cut-off portion is locatedon the rear side in the axial direction as described above, increasingthe length of the sliding surface 924 would simply increase the lengthin the front to back direction (axial direction) of the lifter body 92,leading to bulkiness of the lifter body 92.

The present invention was made in view of such problems and its objectis to provide a roller lifter for internal combustion engines, which hashigher rigidity of the lifter body, prevent cocking in the cylinder, andcan achieve a size reduction.

One aspect of the invention resides in a roller lifter for internalcombustion engines, including

a cylindrical lifter body including a sliding surface on an outercircumferential surface thereof that slides on an inner wall of acylinder; and

a roller rotatably attached to the lifter body via an axial support pinand making contact with a rotating cam lobe;

the lifter body further including a pair of support portions supportingthe axial support pin, the axial support pin being mechanically fastenedto the pair of support portions, with both ends thereof inserted insupport holes formed in the support portions, and an anti-rotationretainer extending radially outward from the sliding surface, wherein

the sliding surface is formed on both front and rear sides in a slidingdirection of the anti-rotation retainer (claim 1).

The anti-rotation retainer in the roller lifter for internal combustionengines extends radially outward from the sliding surface of the lifterbody. Therefore, the lifter body need not be cut off largely to form theanti-rotation retainer. The lifter body can have higher rigidityaccordingly, so that the circularity accuracy of the sliding surface canbe maintained when the axial support pin is mechanically fastened to thesupport portions.

The sliding surface of the lifter body is formed on the front side andthe rear side in the sliding direction of the anti-rotation retainer.Therefore, the distance (sliding length) between the front end and therear end of the sliding surface of the lifter body can be made longer.As a result, the roller lifter can be prevented from cocking relative tothe inner wall of the cylinder.

As the sliding length can be made sufficiently large withoutparticularly increasing the axial length of the lifter body, a sizereduction of the lifter body can also be achieved.

The invention can thus provide a roller lifter for internal combustionengines, which has higher rigidity of the lifter body, prevent cockingin the cylinder, and can achieve a size reduction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a roller lifter in Embodiment 1;

FIG. 2 is a side view of the roller lifter in Embodiment 1;

FIG. 3 is a cross section along A-A of FIG. 2 viewed from the directionof the arrow;

FIG. 4 is a cross section along B-B of FIG. 2 viewed from the directionof the arrow;

FIG. 5 is a cross-sectional diagram illustrating a sliding mechanismwhere the roller lifter is used as a pump lifter in Embodiment 1;

FIG. 6 is a cross-sectional diagram illustrating a sliding mechanismwhere the roller lifter is used as a pump lifter in Embodiment 2;

FIG. 7 is a front view of a roller lifter in Embodiment 3;

FIG. 8 is a side view of the roller lifter in Embodiment 3;

FIG. 9 is a cross section along C-C of FIG. 8 viewed from the directionof the arrow;

FIG. 10 is a front view of a roller lifter in Embodiment 4;

FIG. 11 is a side view of the roller lifter in Embodiment 4; and

FIG. 12 is a front view of a prior art roller lifter.

DESCRIPTION OF THE EMBODIMENTS

The roller lifter for internal combustion engines can be used, forexample, as a pump lifter for a fuel supply pump or a valve lifter for avalve gear in an internal combustion engine such as a car engine.

Herein, one side of the lifter body on which support portions areprovided, i.e., the side that will make contact with the cam lobe, willbe referred to as the rear side in the sliding direction, and theopposite side will be referred to as the front side in the slidingdirection.

The sliding surface may preferably be split into a front sliding surfaceformed on the front side of the anti-rotation retainer and a rearsliding surface formed on the rear side of the anti-rotation retainer,and a small diameter part having a surface recessed radially inward fromthe sliding surface may be formed between the front sliding surface andthe rear sliding surface, with the anti-rotation retainer extending fromthis small diameter part (claim 2).

This allows for highly accurate formation of the sliding surface.Namely, as the front sliding surface and the rear sliding surface areformed to the front and the back of the small diameter part where theanti-rotation retainer is formed, the anti-rotation retainer extendingradially outward from the sliding surface does not get in the of whenmachining these sliding surfaces. The small diameter part, which cannotbe easily polished as the anti-rotation retainer is formed there, neednot be polished, as it is formed radially inward from the slidingsurface and does not contact the inner wall of the cylinder.

The anti-rotation retainer may preferably have a contour formed at leastpartly by punching out part of the lifter body to extend radiallyoutward (claim 3). The anti-rotation retainer can thus be formedintegral with the lifter body by forging. The production cost can bereduced accordingly. Also, punching out part of the lifter body allowsfor highly accurate formation of end faces of the anti-rotationretainer. The anti-rotation retainer can thus provide its function ofstopping rotation effectively.

EXAMPLES Example 1

Specific embodiments of the roller lifter for internal combustionengines will be described below with reference to FIGS. 1 to 5.

The roller lifter 1 for internal combustion engines of this embodimentincludes a cylindrical lifter body 2 having a sliding surface 24 on itsouter circumferential surface that slides on an inner wall 51 of acylinder 5, and a roller 3 rotatably attached to the lifter body 2 withan axial support pin 4 and making contact with a rotating cam lobe 6, asshown in FIGS. 1 and 5.

The lifter body 2 has a pair of support portions 21 for supporting theaxial support pin 4.

Both ends 40 of the axial support pin 4 are inserted in support holes 22formed in the pair of support portions 21 and mechanically fastenedthereto.

The lifter body 2 has an anti-rotation retainer 23 extending radiallyoutward from the sliding surface 24. The sliding surface 24 is formedboth on the front and rear sides in the sliding direction of theanti-rotation retainer 23.

The sliding surface 24 is split into two parts: a front sliding surface241 formed to the front of the anti-rotation retainer 23 and a rearsliding surface 242 formed to the rear of the anti-rotation retainer 23.

A small diameter part 243, where the surface is recessed radially inwardfrom the sliding surface 24, is formed between the front sliding surface241 and the rear sliding surface 242.

The anti-rotation retainer 23 extends from the small diameter part 243,as shown in FIGS. 2 to 4. The anti-rotation retainer 23 has a contourthat is partly formed by punching out part of the lifter body 2 toextend radially outward.

The lifter body 2 is substantially cylindrical, and the sliding surface24 has a cross section that is a perfect circle, or part of a perfectcircle, in a direction orthogonal to the sliding direction.

The rear sliding surface 242 of the sliding surface 24 is formed nearthe rear end of the lifter body 2, while the front sliding surface 241extends from near the front end to around the center of the lifter body2. The small diameter part 243 is formed between the front slidingsurface 241 and the rear sliding surface 242. The small diameter part243 has a length in the sliding direction that is shorter than that ofthe front sliding surface 241 but longer than that of the rear slidingsurface 242. The small diameter part 243 is recessed by about 100 μm ormore, for example, inward relative to the sliding surface 24.

The front end and the rear end of the lifter body 2 are chamfered.

The pair of support portions 21 extends from the rear end of the lifterbody 2 to further than the front end of the small diameter part 243. Thepair of support portions 21 has flat outer surfaces parallel to eachother. The outer surfaces of the support portions 21 are located on aninner side at least than the sliding surface 24.

The anti-rotation retainer 23 is formed in the small diameter part 243.The anti-rotation retainer 23 is formed by forging, such as to punch outpart of the wall that forms the cylindrical lifter body 2. Morespecifically, the rear end in the sliding direction of the anti-rotationretainer 23 is formed continuous with the small diameter part 243, whilethe front end and a pair of side ends are cut out from the smalldiameter part 243. The anti-rotation retainer 23 inclines such that theheight of protrusion increases gradually from the rear end toward thefront end. The front end of the anti-rotation retainer 23 protrudesradially outward from the sliding surface 24. Thus, a front end face 230and part of the pair of side end faces 231 of the anti-rotation retainer23 are exposed from the small diameter part 243.

The sliding surface 24 of the lifter body 2 is polished so as to have aperfect circular outline.

As shown in FIG. 1, the anti-rotation retainer 23 is formed by punchingout part of the small diameter part 243 such as to have a triangularshape, with the side end face 231 extending therefrom, when viewed froma direction orthogonal to the side end face 231.

To assemble the roller 3 to the lifter body 2, as shown in FIGS. 1 to 4,the roller 3 is fitted in between the pair of support portions 21, andthe axial support pin 4 is inserted into the support holes 22 such thatboth ends 40 thereof protrude outward from the pair of support portions21.

The both ends 40 of the axial support pin 4 are then pressed axially bya hydraulic press or the like so that both ends 40 deform to increasetheir diameter, thereby to mechanically fasten the axial support pin 4to the support portions 21.

The roller lifter 1 of this embodiment may be used as a pump lifter 70Afor a fuel supply pump 7A, for example, in an internal combustion enginesuch as a car engine, as shown in FIG. 5.

The roller lifter 1 of this embodiment may be installed, for example,such that the lifter body 2 having the sliding surface 24 slides on theinner wall 51 of a cylinder 5 in the fuel supply pump 7A and that theroller 3 makes contact with a rotating cam lobe 6, as shown in FIG. 5.

The fuel supply pump 7A is configured to compress fuel F supplied from afuel tank (not shown) to feed the compressed fuel F to an injector (notshown) in synchronism with the cam lobe 6 on a cam shaft 61 in areciprocal engine, as shown in FIG. 5.

The pump lifter 70A in the fuel supply pump 7A is configured to slideinside the cylinder 5 arranged in a cylinder head 73 of the reciprocalengine, as the roller 3 is rotated by the rotating cam lobe 6.

The pump lifter 70A is configured to make contact with one end of aplunger 75 arranged slidable inside the cylinder head 73 to slide theplunger 75, to compress the fuel F in a pressure chamber 76 formedinside the cylinder head 73 with the other end 750 of the plunger 75. Asshown in the FIG. 5, the pump lifter 70A (roller lifter 1) is formedwith a plate-like abutting portion 25 inside the lifter body 2 that hasan annular cross-sectional shape.

A retainer 77 is secured to the outer circumference of the plunger 75such as to make contact with the abutting portion 25. A spring 78 isdisposed between the retainer 77 and the cylinder head 73 to bias thepump lifter 70A toward the cam lobe 6.

As shown in the FIG. 5, the anti-rotation retainer 23 of the lifter body2 fits in an anti-rotation groove 53 formed along the axial direction ofthe cylinder 5 in the cylinder head 73 such as to be slidable along thesliding direction.

The pressure chamber 76 is formed midway of a fuel supply passage 79that runs inside the cylinder head 73 such as to communicate the fueltank and the injector.

This embodiment has the following advantageous effects:

The anti-rotation retainer 23 in this embodiment extends radiallyoutward from the sliding surface 24 of the lifter body 2. Therefore, thelifter body 2 need not be cut off largely to form the anti-rotationretainer 23. The lifter body 2 can have higher rigidity accordingly, sothat the circularity accuracy of the sliding surface 24 can bemaintained when the axial support pin 4 is mechanically fastened to thesupport portions 21.

The sliding surface 24 of the lifter body 2 is formed on the front sideand the rear side of the anti-rotation retainer 23 in the slidingdirection of the lifter body 2. Therefore, the distance (sliding length)between the front end and the rear end of the sliding surface 24 of thelifter body 2 can be made longer. As a result, the roller lifter 1 canbe prevented from cocking relative to the inner wall 51 of the cylinder5.

As the sliding length can be made sufficiently large withoutparticularly increasing the axial length of the lifter body 2, a sizereduction of the lifter body 2 can also be achieved.

The sliding surface 24 is split into the front sliding surface 241formed to the front of the anti-rotation retainer 23 and the rearsliding surface 242 formed to the rear of the anti-rotation retainer 23.The anti-rotation retainer 23 extends from the small diameter part 243,which is recessed radially inward from the sliding surface 24 and formedbetween the front sliding surface 241 and the rear sliding surface 242.

This allows for highly accurate formation of the sliding surface 24.Namely, as the front sliding surface 241 and the rear sliding surface242 are formed to the front and the back of the small diameter part 243where the anti-rotation retainer 23 is formed, the anti-rotationretainer 23 extending radially outward from the sliding surface 24 doesnot get in the way of machining these sliding surfaces. The smalldiameter part 243, which cannot be easily polished as the anti-rotationretainer 23 is formed there, need not be polished, as it is recessedradially inward from the sliding surface 24 and does not contact theinner wall 51 of the cylinder 5.

The anti-rotation retainer 23 is formed by punching out part of thelifter body 2 so that its contour partly extends radially outward. Theanti-rotation retainer 23 can thus be formed integrally with the lifterbody 2 by forging. The production cost can be reduced accordingly.

When the anti-rotation retainer 23 is formed, a punch presses part ofthe lifter body 2 from inside and a die with an opening attached on theoutside of the lifter body for the punched portion to escape serves as areceiver. Therefore, the anti-rotation retainer 23 can have shear crosssections as the side end faces 231 and the front end face 230, i.e., theanti-rotation retainer 23 can have highly accurate end faces. Namely, ifpart of the lifter body 2 is protruded radially outward by plasticdeformation instead of by punching to provide the anti-rotation retainer23, the contour of the anti-rotation retainer 23 would take a shape of around boss protruded continuously from the lifter body 2. It would behard to control the contour of the anti-rotation retainer 23, and toachieve a contour exactly as designed to conform to the anti-rotationgroove 53. Therefore, the anti-rotation retainer 23 would have to besubjected to another process such as cutting after the plasticdeformation, in order to suitably function as the anti-rotationretainer.

By punching out part of the lifter body 2 to form part of the contour ofthe anti-rotation retainer 23, the punched-out contour portions (sideend faces 231 and the front end face 230) are cut out from the lifterbody 2 and form shear cross sections. The punched out contour portionswill not be curved, as mentioned above, like a round boss protrudingcontinuously from the lifter body 2. The contour of the anti-rotationretainer 23 is more controllable when forming the anti-rotation retainer23. As a result, the contour of the side end faces 231 and the front endface 230 of the anti-rotation retainer 23 can be easily and accuratelymade into a shape as designed. The anti-rotation retainer 23 can thusexhibit its function of stopping rotation effectively. Moreover, aspunching allows collective formation of a plurality of anti-rotationretainers 23, the number of process steps can also be reduced.

According to this embodiment, as described above, a roller lifter forinternal combustion engines, which has higher rigidity of the lifterbody, prevent cocking in the cylinder, and can achieve a size reduction,can be provided.

Example 2

This embodiment is an example in which the roller lifter 1 is used as avalve lifter 70B in a valve gear 7B of a reciprocal engine.

The roller lifter 1 itself is configured the same as the roller lifter 1of Embodiment 1.

The valve lifter 70B in the valve gear 7B is configured to slide insidea cylinder 5 arranged in a cylinder head 73 of the reciprocal engine, asthe roller 3 is rotated by the rotating valve gear cam lobe 6 formed ona cam shaft 61 of the reciprocal engine, as shown in FIG. 6.

The valve lifter 70B abuts on a stem distal end 732 of a valve 730 inthe reciprocal engine, and is arranged slidable up and down inside thecylinder 5 such as to open and close the valve 730 disposed to open andclose an intake/exhaust port (intake port or exhaust port) 733.

An abutting portion 25 is configured to abut on the stem distal end 732of the valve 730.

A retainer 77 is secured to the outer circumference of a stem part 731of the valve 730. A spring 78 is disposed between the retainer 77 andthe cylinder head 73 to bias the valve lifter 70B toward the cam lobe 6.

The rest is the same as Embodiment 1, with similar advantageous effects.

Example 3

As shown in FIGS. 7 to 9, this embodiment is an example of the rollerlifter 1, in which one end in a direction orthogonal to the slidingdirection of the anti-rotation retainer 23 is continuous with the smalldiameter part 243 while the other end extends radially outward from thesliding surface 24.

The roller lifter 1 of this embodiment has a pair of anti-rotationretainers 23. The respective ends of the anti-rotation retainers 23 thatare continuous with the small diameter part 243 face each other, whilethe other ends (side end faces 231) are oriented to mutually oppositedirections.

The side end faces 231 are formed such as to face the inner side face ofthe anti-rotation groove 53 (see FIG. 5) when the roller lifter 1 ismounted to the cylinder 5.

The rest is the same as Embodiment 1, with similar advantageous effects.

Example 4

As shown in FIGS. 10 and 11, this embodiment is an example of the rollerlifter 1, in which the small diameter part 243 is formed on the frontside in the sliding direction of the support portions 21 of the lifterbody 2. One end in a direction orthogonal to the sliding direction ofthe anti-rotation retainer 23 is continuous with the small diameter part243, while the other end extends radially outward from the slidingsurface 24.

The front sliding surface 241 of the roller lifter 1 of this embodimentis formed shorter than the rear sliding surface 242.

The rest is the same as Embodiment 3, with similar advantageous effects.

1. A roller lifter for internal combustion engines, comprising: acylindrical lifter body including a sliding surface on an outercircumferential surface thereof that slides on an inner wall of acylinder; and a roller rotatably attached to the lifter body via anaxial support pin and making contact with a rotating cam lobe; thelifter body further including a pair of support portions supporting theaxial support pin, the axial support pin being mechanically fastened tothe pair of support portions, with both ends thereof inserted in supportholes formed in a pair of support portions, and an anti-rotationretainer extending radially outward from the sliding surface, whereinthe sliding surface is formed on both front and rear sides in a slidingdirection of the anti-rotation retainer.
 2. The roller lifter forinternal combustion engines according to claim 1, wherein the slidingsurface is split into a front sliding surface formed on a front side ofthe anti-rotation retainer and a rear sliding surface formed on a rearside of the anti-rotation retainer, and wherein a small diameter parthaving a surface recessed radially inward from the sliding surface isformed between the front sliding surface and the rear sliding surface,the anti-rotation retainer extending from this small diameter part. 3.The roller lifter for internal combustion engines according to claim 1,wherein the anti-rotation retainer has a contour formed at least partlyby punching out part of the lifter body to extend radially outward.